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SubjectRe: [PATCH v1 2/2] drm/sprd: fix potential NULL dereference
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Hi,

on the changes for platform_get_resource(), you can

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

but see my comments below.

Am 24.12.21 um 15:12 schrieb Kevin Tang:
> platform_get_resource() may fail and return NULL, so check it's value
> before using it.
>
> 'drm' could be null in sprd_drm_shutdown, and drm_warn maybe dereference
> it, remove this warning log.
>
> Cc: Orson Zhai <orsonzhai@gmail.com>
> Cc: Chunyan Zhang <zhang.lyra@gmail.com>
> Signed-off-by: Kevin Tang <kevin.tang@unisoc.com>
> ---
> drivers/gpu/drm/sprd/sprd_dpu.c | 3 +++
> drivers/gpu/drm/sprd/sprd_drm.c | 8 ++------
> drivers/gpu/drm/sprd/sprd_dsi.c | 3 +++
> 3 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/sprd/sprd_dpu.c b/drivers/gpu/drm/sprd/sprd_dpu.c
> index 06a3414ee..69683b7ba 100644
> --- a/drivers/gpu/drm/sprd/sprd_dpu.c
> +++ b/drivers/gpu/drm/sprd/sprd_dpu.c
> @@ -790,6 +790,9 @@ static int sprd_dpu_context_init(struct sprd_dpu *dpu,
> int ret;
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -EINVAL;
> +

You can add an error message if this fails.


> ctx->base = devm_ioremap(dev, res->start, resource_size(res));
> if (!ctx->base) {
> dev_err(dev, "failed to map dpu registers\n");
> diff --git a/drivers/gpu/drm/sprd/sprd_drm.c b/drivers/gpu/drm/sprd/sprd_drm.c
> index a077e2d4d..54030839e 100644
> --- a/drivers/gpu/drm/sprd/sprd_drm.c
> +++ b/drivers/gpu/drm/sprd/sprd_drm.c
> @@ -154,12 +154,8 @@ static void sprd_drm_shutdown(struct platform_device *pdev)
> {
> struct drm_device *drm = platform_get_drvdata(pdev);
>
> - if (!drm) {
> - drm_warn(drm, "drm device is not available, no shutdown\n");
> - return;
> - }
> -
> - drm_atomic_helper_shutdown(drm);
> + if (drm)
> + drm_atomic_helper_shutdown(drm);

This change should be in a separate patch. Instead of removing the
warning, you should rather use dev_err() or dev_warn() from [1]. Not
being able to shut down here looks like a serious driver bug that the
user should know about.


> }
>
> static const struct of_device_id drm_match_table[] = {
> diff --git a/drivers/gpu/drm/sprd/sprd_dsi.c b/drivers/gpu/drm/sprd/sprd_dsi.c
> index 911b3cddc..955c5995a 100644
> --- a/drivers/gpu/drm/sprd/sprd_dsi.c
> +++ b/drivers/gpu/drm/sprd/sprd_dsi.c
> @@ -907,6 +907,9 @@ static int sprd_dsi_context_init(struct sprd_dsi *dsi,
> struct resource *res;
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -EINVAL;
> +

Again, an error message seems appropriate.

Best regards
Thomas

[1]
https://elixir.bootlin.com/linux/latest/source/include/linux/dev_printk.h#L145

> ctx->base = devm_ioremap(dev, res->start, resource_size(res));
> if (!ctx->base) {
> drm_err(dsi->drm, "failed to map dsi host registers\n");

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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